Add a Rubocop rule for lazy-loaded root types

lib/graphql/rubocop.rb

@@ -3,3 +3,4 @@
 require "graphql/rubocop/graphql/default_null_true"
 require "graphql/rubocop/graphql/default_required_true"
 require "graphql/rubocop/graphql/field_type_in_block"
+require "graphql/rubocop/graphql/root_types_in_block"

lib/graphql/rubocop/graphql/root_types_in_block.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+require_relative "./base_cop"
+
+module GraphQL
+  module Rubocop
+    module GraphQL
+      # Identify (and auto-correct) any root types in your schema file.
+      #
+      # @example
+      #   # bad, immediately causes Rails to load `app/graphql/types/query.rb`
+      #   query Types::Query
+      #
+      #   # good, defers loading until the file is needed
+      #   query { Types::Query }
+      #
+      class RootTypesInBlock < BaseCop
+        MSG = "type configuration can be moved to a block to defer loading the type's file"
+
+        def_node_matcher :root_type_config_without_block, <<-Pattern
+        (
+          send nil? {:query :mutation :subscription} const
+        )
+        Pattern
+
+        def on_send(node)
+          root_type_config_without_block(node) do
+            add_offense(node) do |corrector|
+              new_node_source = node.source_range.source
+              new_node_source.sub!(/(query|mutation|subscription)/, '\1 {')
+              new_node_source << " }"
+              corrector.replace(node, new_node_source)
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/fixtures/cop/.rubocop.yml

@@ -16,3 +16,9 @@ GraphQL/FieldTypeInBlock:
   Include:
     - field_type.rb
     - field_type_autocorrect.rb
+
+GraphQL/RootTypesInBlock:
+  Enabled: true
+  Include:
+    - root_types.rb
+    -  root_types_autocorrect.rb

spec/fixtures/cop/root_types.rb

@@ -0,0 +1,5 @@
+class MyAppSchema < GraphQL::Schema
+  query Types::Query
+  mutation Types::Mutation
+  subscription Types::Subscription
+end

spec/fixtures/cop/root_types_corrected.rb

@@ -0,0 +1,5 @@
+class MyAppSchema < GraphQL::Schema
+  query { Types::Query }
+  mutation { Types::Mutation }
+  subscription { Types::Subscription }
+end

spec/graphql/cop/root_types_in_block_spec.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+require 'spec_helper'
+
+describe "GraphQL::Cop::RootTypesInBlock" do
+  include RubocopTestHelpers
+
+  it "finds and autocorrects field corrections with inline types" do
+    result = run_rubocop_on("spec/fixtures/cop/root_types.rb")
+    puts result
+    assert_equal 3, rubocop_errors(result)
+
+    assert_includes result, <<-RUBY
+  query Types::Query
+  ^^^^^^^^^^^^^^^^^^
+    RUBY
+
+    assert_includes result, <<-RUBY
+  mutation Types::Mutation
+  ^^^^^^^^^^^^^^^^^^^^^^^^
+    RUBY
+
+    assert_includes result, <<-RUBY
+  subscription Types::Subscription
+  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    RUBY
+
+    assert_rubocop_autocorrects_all("spec/fixtures/cop/root_types.rb")
+  end
+end